Telephone system



Nov. 2l, 1933. o. c. LEVY7 TELEPHONE SYSTEM Filed Nov. so, 1931 PATENT'A OFFICE TELEPHONE SYSTEM Oscar C. Levy, Chicago, Ill., assignery toAssociated Electric Laboratories, Inc., Chicago, Ill., a corporation ofDelaware Application November 30, 1931 Serial No. 577,971

13 Claims.

This invention relates to automatic telephone systems in general, butrelates more particularly to small systems of the character commonlyknown as private automatic exchanges. These systems are as a ruleprivately owned by individuals or corporations and are installed infactories and other establishments for providing ,local service betweena small number of local telephone lines.

The object of the invention is to provide means whereby a minimum numberof switching `devices will be employed for completing the desiredtelephone connections, and which will enable the equipment to bemanufactured very cheaply while retaining all the features necessary formodern high-class and dependable telephone service.

One of the features of the invention relates to the improved circuitarrangements of a finderconnector link circuit comprising a numericalforward selecting switch for connecting with a called line and anon-numerical line finder switch for finding the callLng line.

Another feature of the invention is the provision 'of circuitarrangements whereby a relay first functions as an interrupterstepping-relay for the finder switch magnet, then functions as atest-stop relay when the finder finds the calling line, and then laterfunctions as a line pulsing relay for directively operating theconnector of the finder-connector link.

Another feature of the invention relates to an improved switch-throughcircuit which enables a straight multiple to be used between the banksof the hunting finder and the connector.

Other features, together with the ones named above, will be explainedhereinafter, reference being had to the accompanying drawing which showsby means of the usual circuit diagrams a sufficient amount of apparatusto enable the invention to be understood.

The drawing diagrammatically shows two automatic substations, A and A',together with their individual cut-off relays 4 and 64, a line relay 22,and an all-trunks-busy relay 23, which are common to all the subscriberslines, and a finder-connector link circuit. The line circuit of eachsubscribers line terminates in the banks of the finders, such as thefinder F, and in the banks of the connectors, such as the connector C.The automatic substations A and A are similar to each other, and eachhas the usual signalling, talking, and switch-controllinginstrumentalities.

The mechanism of the finders, such as F, and the connectors, such as C,is of the well-known rotary type, commonly used for rotary lineswitches,and the wipers of which move in a forward direction only and remain inthe position last used. The circuit details of the connector aresomewhat different from the finders in that the wipers of the connectorare directively operated to a called line and are automatically restoredto normal position after termination of the conversation.

In the case illustrated, Applicant has elected to show a system having amaximum of twentytwo local lines having telephone numbers l to 9, 01 to09, and 001 to 004. The lines 1 to 9 terminate in the first ninecontacts accessible to the wipers of the connectors, the lines 01 to 09terminate in the eleventh to the nineteenth contacts accessible to thewipers of the connectors, and the lines 001 to 004 terminate in thetwenty-first to the twenty-fourth contacts accessible to the wipers ofthe connectors. The tenth and twentieth contacts are left dead while thetwenty-fifth contact is used for normal position of the connectorwipers.

The subscribers cut-off relays, such as 4 and 64, and relay 14, aretwo-step relays which close their contacts marked I in their first stepand their contacts marked II in their second step. Relay l2 is asloW-to-operate relay which is also appreciably slow to release. Relay13 is equipped with a copper sleeve around its core which renders therelay slow, to release.

Having briefiy described the apparatus involved in a system of thistype, a detailed description of the operation will n ow be given. Forthis purpose, it willl be assumed that subscriber A wishes to obtainconnection with subscriber A'. When subscriber A removes his receiver toinitiate a call, a circuit is completed for the common line relay 22 andcutoff relay 4 as follows: from ground at all armatures 37 in' normalposition, common conductor 26, winding of common line relay 22, commonconductor 3, armature 5, conductor 2, through the calling substationloop, conductor 1, armature 7, and through the lower winding of cut-0Erelay 4, to battery. Cut-off relay 4 is so adjusted that when thecircuit is closed through the lower winding armature 6 is the onlyarmature operated. Relay 4 in operating its armature 6 marks the line ascalling by connecting battery through its upper winding to thefinderbank, and prepares a circuit for fully energizing itself over its'upperwiper when the finder finds the calling line. Common line relay 22 isoperated over the above traced circuit and closes a circuit for a startrelay of an idle finderconnector link as follows: ground by way ofarmature 79, start lead 25, winding of slow-to-operate start relay 12,armature 42, twenty-fifth bank contact and wiper 62, interrupter springsof the connector motor magnet 21 and through the winding of magnet 21,to battery. Due to the high resistance of relay 12 the motor magnet 21is not energized over this circuit, but start relay 12 energizes tostart the finder.

In case this finder-connector link is busy, then armature 42 would beopened and the wiper 62 would not be in normal position; therefore, thestart circuit would extend to the next nder connector link by way ofamature 31 and conductor 24. In case all of the nder-connector links arebusy when a subscriber initiates a call, then the circuit for shuntingall-trunks-bimy relay 23 is opened at the armatures 37 of the busylinderconnector links and a circuit may be traced from ground throughwinding of relay 23, winding of relay 22, and thence over the abovetraced circuit to battery through the lower winding of the cutott relayassociated with the calling line. Due to the high resistance of relay23, the subscribers cut-ofi' relay and relay 22 are not energized. Relay23, however, energizes and at armature 69 connects the busy tone to thecalling subscribers line by way of conductor 3. The calling subscriberwill then replace his receiver and call again after an interval.

Returning now to when start relay 12 was energized in response tosubriber A initiating a call, said relay at amature 30 prepares the testcircuit for relays 14 and 15, at amature 31 opens the start circuitextending to the next ilnder-connector link, at armature 33 prepares acircuit for relay 15, and at armature 32 closes a circuit extending fromarmature 43 and its resting contact for energizing the nder motor magnet20. Magnet 20 energizes to position its pawl preparatory to stepping thewipers of the ilnder and near the end of its stroke closes armature 34to complete a circuit for energizing relay 15 by way of armature 33.Relay 15 energizes and at armature 43 opens the circuit extending tomagnet 20 which deenergizes and operates the wipers of the finder onestep. 'Ihe deenergization of magnet 20 also opens the circuit of relay15 at armature 34, and the latter relay deenergizes to again close thecircuit to the motor magnet. This interaction between relay 15 andmagnet 20 continues until test wiper 9 encounters a calling batterypotential. When wiper 9 reaches the contact marked with calling batterypotential a circuit may be traced for holding relay 15 energized and forenergizing relay 14 as follows: from ground by way of the upper windingof relay 15, normally closed springs controlled by amature 38, upperwinding of two-step relay 14, armature 30, test wiper 9 and engaged bankcontact, armature 6 and through the upper winding of cut-ol! relay 4, tobattery. The relay 15 is held energized over this circuit in .order toprevent the magnet from energizing to step the wipers another step.CutoiI relay 4 energizes in its second step over the above-tracedcircuit. Two-step relay 14 energizes in its first step over theabove-traced circuit to close only armature 40, which completes acircuit for energizing slow-to-release relay 13 by way of the workingcontact of armature 43. Slow-to-release relay 13 at amature 37 removesone o1' the ground connections for shunting relay 23, at armature 36prepares a point in the talking circuit as well as preparing a point inthe impulsing circuit for relay 15, at armature 35 prepares a circuitfor series relay 16, and at armature 34 grounds hold conductor 29 andcompletes a circuit through the lower winding of two-step relay 14 forenergizing said'relay through its second step to operate armatures 38,39, 41, and 42. At the normally closed springs controlled by armature 38relay 14 opens the test circuit including the upper windings of relays14 and 15, but these relays do not deenergize at this time because relay14 is held over its lower winding while the subscribers calling loop isnow connected in bridge of both windings of relay 15 to prevent itsdeenergization. At armature 39 relay 14 grounds wiper 9 to fullyenergize cut-off relay 4 in its second step and to make this line busyto both finder and connector switches, at armature 41 and its restingcontact opens the restoring circuit of the connector, and at its workingcontact prepares a point in the impulsing circuit to the connector motormagnet 21. At armature 42 relay 14 opens the circuit of start relay 12,which deenergizes after a short interval to close the start circuit toanother nder-connector link at armature 31, to open the circuit to thefinder magnet 20 at armature 32, and to open the circuit to the lowerwinding of relay 15 at armature 33. Cut-oil relay 4, upon energizing inits second step, disconnects the line conductors 1 and 2 from the lowerwinding of relay 4 and from common line relay 22, which deenergizes incase no other subscriber is initiating a call.

All of the operations just described has taken place responsive to thesubscriber at substation A removing his receiver, and at this time dialtone is transmitted from conductor 28, normal cbntact and wiper 60,resting contact of armature 51 and said armature, the condenser, andthence over the calling subscriber's loop in the well-known manner.

Subscriber A may now dial the number of the desired subscribers line, inthis case number 05, 105 since subscriber A' is the desired subscriberand such subscribers line terminates in the fifteenth set of bankcontacts accessible to the connector wipers.

Subscriber A will therefore dial the digits 110 and Responsive to theoperation of the calling device CD at substation A for the first digit,the circuit extending to relay is opened ten times to deenergize relay15 a corresponding number of times. At each deenergization of relay 15the circuit of slow-to-release relay 13 is momentarily opened atarmature 43 and its working contact, but said relay, dueto the coppersleeve around its relay core, maintains its armatures attracted duringthe impulsing period. 120 Each time relay 15 deenergizes, a circuit maybe traced from grounded armature 43 and its resting contact, armature 41and its working contact, armature 53, armature 58, and through thewinding of magnet 21 to battery for energizing magnet 21 to operate itspawl preparatory to stepping the wipers of the connector. A branch ofthe above-traced circuit extends by way of armature to the lower windingof series relay 16 for energizing the latter relay. Relay 16 at 130armature 44 opens a point in the circuit of switching relay 19, atarmature 45 prepares a point in the circuit of busy relay 18, atarmature 46 closes a short circuit around its upper winding to makerelay 16 slow to release and so that 135 it will maintain its armaturesattracted during the impulsing period, and at armature 47 prepares a newimpulsing circuit for magnet 21 independent of armature 53 which may beoperated by busy relay 18 operating in response to test Wiper 61 passingover busy grounded contacts. After the rst impulse line relay 15reenergizes and opens the circuit of magnet 21 which releases and stepsthe wipers one step. The remaining impulses of the rst digit operate theline relay 15 and magnet 21 in the manner set forth to position thewipers to 63, inclusive, on the tenth set of bank contacts. Since thesecontacts are left dead the wipers merely come to rest thereon until thesecond digit is dialled.

Responsive to subscriber A dialling the second digit, or digit 5 in thiscase, line relay 15, series relay 16, and magnet 21 operate in the samemanner as previously set forth to position the wipers on the fifteenthset of bank contacts, or the contacts terminating the line of substationA'.

Assuming that substation A' is busy, then wiper 61 will encounter aground connection on the fifteenth bank contact placed thereon by afinder or connector of another finder connector link. In this case busyrelay 18 is energized over a circuit extending from the busy groundedcontact, wiper 61, armature and its working contact, and through thewinding of busy relay 18, to battery. Busy relay 18, upon energizing, atarmature 52 prepares a locking circuit for itself, at armature 53 opensa point in the initial impulsing circuit to magnet 2l, and at amature 51completes a circuit for transmitting busy tone over the talkingconductors and ring-back condenser RBC, to subscriber A. A short timeafter the transmission of the last digit, series relay 16 deenergizes,and at the normally closed contacts controlled by armature 45 completesthe locking circuit of busy relay 18 as follows: from grounded conductor29, armature 52 and its working contact, normally closed springscontrolled by armature 45, and through the winding of relay 18, tobattery. When subscriber A hears the busy tone such subscriber willreplace the receiver and release the connection in the same manner aswill be described hereinafter.

Assuming now that substation A is idle instead of busy, then wiper 61will not encounter a grounded contact, and, therefore, busy relay 18will not be energized. Therefore, when relay 16 denergizes after theimpulsing period, a circuit may be traced for energizing switching relay19 to close its armatures 55 and 56 and for energizing cut-oif relay 64in its first step to close armature 66 as follows: from groundedconductor 29, armature 52 and its resting contact, armature 44, lowerwinding of switching relay 19, resting contact of armature 59 and saidarmaf ture, lower talking conductor, wiper 63, conductor 71. armature67, andthrough the lower winding of cut-off relay 64, to battery.

Cut-off relay 64 closes only its contacts 66 and switching relay 19 isadjusted to close only its armatures 55 and 56 at this time. When relay19 closes its armature 55 a circuit may be traced` for energizing relay64 in its second step as follows: from grounded conductor 29, armature55, wiper 61 and engaged contact, armature 66 and through the upperwinding of relay 64, to battery. Relay 64 is fully operated over thiscircuit to operate its armatures and 67 to disconnect the lineconductors and 71 from start conductor 3 and the lower winding of relay64. At armature 56 relay 19 closes a circuit from grounded conductor 29through its upper winding for fully operating its remaining armatures.Relay 19, upon fully operating, at armature 57 opens a point in therestoring circuit of the connector, at armature 58 opens a point in theimpulsing circuit to magnet 21, and at armatures 54 and 59 connectsgenerator GEN to the called line as follows: from ground at armature 48,armature 54, wiper 60 and engaged bank contact, conductor 70,switchhook, condenser and ringer at substation A', conductor 71, wiper63, armature 59 and its working contact, armature 50 and its restingcontact, and through the lower winding of ring-cut-off relay 17 tointerrupted generator GEN. When subscriber A answers by removing hisreceiver, the ring-cut-oi' relay 17 is energized over the substationloop and the circuit just traced. At armatures 48 and 50, relay 17disconnects the ringing circuit and completes the talking circuit by wayof the working contacts of armatures 48 and 50, and at armature 49completes a locking circuit for itself to grounded conductor 29. Thecalling subscriber A and called subscriber A' are connected over theheavy talking conductors, each subscriber receiving talking battery fromthe windings of line relay 15.

After conversation and responsive to subscribers A and A replacing theirreceivers, line relay 15 deenergizes and at armature 43 opens thecircuit of release relay 13, which deenergizes after a short interval.At armature 34 release relay 13 opens the locking circuits of relays 4,14, 17, 19, and 64, and busy relay 18 in case of a busy call, whereuponsaid relays deenergze. A circuit may now be traced for restoring thewipers of the connector to normal as follows: from grounded armature 43and its resting contactarmature 41 and its resting contact, multipledcontacts engaged by wiper 62 and said wiper, interrupter springs ofmagnet 21 and through the winding of magnet 21, to battery. Magnet 21operates like a buzzer over the above-traced circuit until wiper 62 nolonger engages a grounded contact, at which time the wipers of theconnector stop and remain in normal position or the position shown inthe drawing. The wipers of the finder remain in the positions last used,and, therefore, when the connector wipers reach their normal positionsthe lnder-connector link is available for another call.

The operation of the finder-connector link 110 for subscribers havingtelephone numbers 1 to 9, inclusive, is the same as that previouslydescribed with the exception that only one digit is dialled instead oftwo. In order to call a subscriber having telephone numbers from 001 to004, inclusive, 'T15 three digits are dialled by the calling subscriberto set the connector on dead bank contacts responsive to the rst twodigits, after which the last digit may be dialled to connect with thedesired subscribers line. Y

Having described the invention, what is considered to be new and isdesired to have protected by Letters Patent will be set forth in thefollowing claims:

What is claimed is:

1. In a telephone system, a link circuit comprising a nder switch and aconnector switch, Wipers on said switches, subscribers lines accessibleto said wipers, and means including a combined stepping, test, andline-pulsing relay for automatically stepping the wipers of the finder,for automatically stopping the wipers of the finder when the callingline is found, and for directively stepping the wipers of the connectorto a desired called line.

2. In a telephone system, a link circuit comprising a finder switch anda connector switch, wipers on said switches, subscribers linesaccessible to said wipers, a relay in said link circuit, means forintermittently operating said relay to operate said finder wipersstep-by-step in search of a calling line, a test circuit completed formaintaining said relay energized responsive to the finder wipers'finding the calling line to prevent further operation of said iinderwipers, and means for directive- 1.2. ly operating said relay todirectively operate the connector wipers to a desired called line.

3. In a telephone system, a link circuit comprising a finder switch anda connector switch, wipers..

on said switches, subscribers lines accessible 1:6150- said wipers, amotor magnet in said link for operating the wipers of said finder,a-relay in said link circuit, means for energizing the finder magnet,means controlled by the energization of said finder magnet forenergizing said relay, means controlled by the energization of saidrelay for deenergizing said magnet to step the finder wipers and todeenergize said relay whereby said magnet and relay intermittentlyoperate to advance the wipers of the iinders step by step in search ofthe calling line, a test circuit completed responsive to the wipers ofthe nder finding the calling line for maintaining said relay energizedto maintain the wipers of the finder on the calling line, means operatedresponsive to the finder finding the calling line for connecting saidrelay in bridge of the calling line, subscriber-controlled means forthereafter directively operating said relay responsive to impulsestransmitted over the calling liner and a motor magnet in said linkcircuit directively operated by said relay to step the wipers of theconnector to a desired called line in response to said impulses.

4. In a telephone system, a switch having wipers, subscribers lines eachincluding a pair of talking conductors and a test conductor terminatingin the banks of said switch, means for operating the wipers of saidswitch to engage the conductors of one of said subscribers lines, aswitching relay in said switch and a line cut-off relay individual tosaid subscribers line partially operated over a circuit including one ofthe talking conductors of said subscribers line in response to saidengagement, contacts on said relays operated responsive to the partialoperation of said relays for closing circuits for fully operating saidrelays, the circuit for fully energizing said cutoff relay including thesubscribers test conductor, and other contacts on said relays operatedin response to the full operation of said relays for completing atelephone connection to the subscriber over the subscribers talkingconductors.

5. In a. telephone system, a switch having wipers, subscribers lineseach including a pair of talking conductors and a test conductorterminating in the banks of said switch, means for operating the wipersof said switch to engage the said conductors of a subscribers line,means only partially operated over one of the talking conductors of saidsubscribers line in response to said engagement for completing anoperating circuit over said subscribers test conductor, and said meansthereafter fully operated over said test conductor'to cause said switchto switch through and complete a connection to said subscribers line.

6. In a telephone system, a switch having wipers, subscribers lines eachincluding a pair of talking conductors and a test conductor terminatingin the banks of said switch, means for operating the wipers of saidswitch to engage the conductors of one of said subscribers lines, a linecut-otr relay individual to said subscribers line partially operatedover a circuit including one of the talking conductors of saidsubscribers line in response to said engagement to connect said relay tosaid subscribers test conductor, and means for thereafter fullyoperating said relay over a circuit including the test conductor of saidsubscribers line.

7. In a telephone system, a link circuit comprising an automaticallyoperated hunting finder switch and a directively operated connectorswitch, subscribers lines each including a pair of talking conductorsand a test conductor terminating in the bank contacts of said connectorswitch, and straight multiple connections connecting the conductors ofsaid subscribers' lines terminating inl the bank contacts of saidconnector switch to corresponding bank contacts in said finder switch.

8. In a telephone system, a plurality of subscribers lines, a pluralityof finders having access to said subscribers lines, a relay common tosaid lines and finders, a short circuit around said relay closed by eachfinder in normal position, means for removing said short circuit fromaround said relay only when all said finders are busy, means forthereafter energizing said relay responsive to one of said subscribersinitiating a call at a time when all said finders are busy, and contactson said relay for connecting a busy tone source to said calling line.

9. In a telephone system, a plurality of subscribers lines, a pluralityof finders having access to said lines, a relay common to said lines andfinders normally inoperative as long as any one of said finders is idle,means for operating said relay in response to one of said subscribersinitiating a call only in case all of said nders are busy. and contactson said relay for connecting a busy tone source to said calling line.

10. In a telephone system, a plurality of subscribers lines, a pluralityof finders having access to said lines, a start relay, a busy relay, anda start conductor common to said lines and nders, said relays connectedin a series circuit to said start conductor, means for energizing onlysaid start relay over said conductor responsive to one of saidsubscribers initiating acall, means controlled by said start relay forstarting an idle one of said finders to find the calling line, means forenergizing only said busy relay over said conductor responsive to one ofsaid subscribers initiating a call when all said finders are in use, andmeans controlled by said busy relay for connecting a busy tone source tosaid calling subscribers line over said conductor.

l1. In a telephone system, subscribers lines, switches for use bycalling subscribers for extending a connection in the direction of acalled line, other switches for use in completing connections to calledlines, a pair of talking conductors and a test conductor for eachsubscribers line terminating in the bank contacts of said otherswitches, and straight multiple connections connecting the conductors ofsaid subscribers lines terminating in the bank contacts of said otherswitches to corresponding bank contacts in said first switches.

' l2. In a telephone system, a non-numerical hunting switch, adirectively operated connector switch, subscribers lines each includinga pair of talking conductors and a test conductor terminating in thebank contacts of said connector switch, and straight multipleconnections connecting the conductors of said subscribers' linesterminating in the bank contacts of said connector switch tocorresponding bank contacts in said non-numerical hunting switch.

13. In a telephone system, a plurality of link circuits each comprisinga finder switch and a connector switch, a start relay individual to eachfinder switch, and a start circuit for each start relay including awiper of the associated connector switch.

0 OSCAR C. LEVY.

